The present invention relates to a fuel pump for fuel supply of an internal combustion engine and, more particularly, to a high pressure fuel pump used for a fuel injection system of a so-called direct fuel injection type internal combustion engine, which system injects directly fuel from a fuel injection valve mounted on a combustion chamber into the combustion chamber.
For an internal engine in which fuel is directly injected into the combustion chamber, it is necessary to have a high pressure pump for raising the pressure of fuel to be supplied to an fuel injection valve to a pressure of 2 MPa or more.
As such a high pressure pump, there has been known a conventional axial plunger pump which is disclosed in JP A 9-236080. Such a conventional axial plunger pump is constructed so as to partition a driving mechanism part lubricated with oil and a pump chamber compressing and discharging fuel by a metal bellows.
Further, a conventional high pressure fuel pump disclosed in JP A 9-250447 is constructed so as to circulate fuel also to a sliding portion of a driving mechanism part, and the driving mechanism part, that is, the sliding portion is lubricated with fuel.
The above-mentioned conventional high pressure fuel pumps have the following problems or disadvantages.
1. The former conventional pump has a problem that the pump is large-sized because of use of the metal bellows and it is difficult to make the pump size small because it is necessary to provide a seal portion on a bellows mounting portion.
2. In the latter conventional pump, it is not necessary to provide any bellows, however, lubrication is insufficient because the sliding portion of the driving mechanism part is lubricated with fuel of low viscosity.
An object of the present invention is to provide an axial plunger pump in which any bellows is unnecessary and lubrication of a sliding portion of a driving mechanism part is sufficient.
Another object of the present invention is to enable a roll bearing to be used in the driving mechanism part.
In order to solve the above problems, an axial plunger pump according to the present invention is constructed so as to comprise a shaft having a swash plate effecting swing motion and transmitting driving force from the outside, plungers each reciprocating by the swing motion of the swash plate, a cylinder block having cylinders formed so as to open on the side of the swash plate and inserting therein the plungers and having passages for supplying fuel to the cylinders, a body combined with the cylinder block to enclose the swash plate, and sealing members arranged between the plungers and the cylinders on the swash plate side of the passages formed in the cylinder block for sealing gaps between the plungers and the cylinders, respectively.
Another invention is a high pressure fuel pump which comprises a shaft having an swash plate effecting swing motion, and transmitting driving force from the outside, a plurality of plungers each reciprocating by the swing motion of the swash plate a cylinder block having cylinders formed so as to open on the side of the swash plate and inserting therein the plungers, the cylinder block having passages for supplying fuel to the cylinders, a body combined with the cylinder block to enclose the swash plate, a radial bearing supporting the shaft mounted on the body and a bearing arranged on the back of the swash plate for supporting an axial load applied on the swash plate, which bearing is a thrust roll bearing having rolls or balls larger in rolling pitch diameter than the radial bearing.
Still another invention is a plunger for a high pressure fuel pump, which plunger has a radial hole traversing the central axis of the plunger, a groove formed on the periphery so as to overlap with the radial hole and having a prescribed axial length, and an end portion to which an axial hole communicating with the radial hole is opened and the other end portion is formed spherical.